Construction methods using cementitious grouting materials are being employed not only for foundation treatment of dams, prevention of ground liquefaction, and reinforcement of rock and ground in tunnel excavation, but also as a filling material for fixing anchor bolts, recently.
As cementitious grouting materials, for making the grouting more effective, fine particles grouting materials having a Blaine specific surface area of 5000 cm2/g or more obtained by pulverizing and classifying a mixture consisting of blast-furnace slag mainly and Portland cement are used, and there are many examples using such materials.
Fine particle grouting materials having a fine particle size has high hydration activity. Since the viscosity of the grouting material slurry increases due to hydration, expected grouting effects often fail to be exhibited. Also, to ensure the filling effect, it is necessary to maintain a low viscous state for a long period of time. For this reason, high-level dispersion of particles and inhibition of hydration are required. As such dispersion, a high-performance water-reducing agent is widely used (e.g., see Laid-Open Japanese patent publication No. 2003-49164; Patent Document 1).
Fine particle grouting material develops strength equivalent to that of Portland cement. However, due to the use of the high-performance water-reducing agent, the gelation and hardening after injection may be retarded and take 10 to 20 hours in some cases.
The grouting material slurry of injected grout may fail to obtain sufficient effects of the grouting material in a case either where it receives an external force before gelation or hardening or where it contacts with confined water or running water to be removed and washed away from the injected area. And also if hardening of the grouting material is markedly delayed, the whole construction process including the step next to grouting is disturbed, which may lead to economical disadvantages.
On the other hand, as a grouting for limited area, a grouting material composition to which gel time is imparted using a specific rapid-hardening admixture, inorganic sulfuric acid salt and liquid glass is devised for the purpose of shortening the setting time (Laid-open Japanese patent publication No. 2004-231884; Patent Document 2). Such a grouting material has, however, problems that development of strength is insufficient and that a low viscous state cannot be maintained due to high hydration rate.
[Patent Document 1 ] Laid-open Japanese patent publication No. 2003-49164
[Patent Document 2] Laid-open Japanese patent publication No. 2004-231884